Composite multi-pressure gasket

#The present invention relates to a composite gasket comprising an elastomeric portion and a hard plastic non-elastomeric portion for forming a groove in a plastic pipe bell and for providing a secure seal between the bell and a spigot. Additionally, the present invention relates to an improved pipe joining system including the composite gasket.

#In plastic pipe systems, connections between the various components must be sealed to prevent escape of fluids from the connections. The connections typically comprise an enlarged bell which receives a spigot. The spigot and bell can be formed as segments of pipe lengths or connecting members, such as elbows, T's, etc. In this application, the terms "fitting" and "pipe" are intended to include both pipe lengths and connecting members.

#The seal between the bell and spigot is conventionally provided by a gasket mounted in one of the components of the connection and sealingly and resiliently engaging the other component. Most often, the seal is mounted in the bell and has at least one radially inwardly projecting sealing lip which is engaged and deformed by the spigot such that a tight interference fit is formed between the spigot and sealing lip to prevent the escape of fluid.

#Referring to the drawings which form a part of this disclosure:

#FIG. 1 is a perspective view of a molded and fused composite hard plastic/elastomeric gasket in accordance with a first embodiment of the present invention;

#FIG. 1A is a perspective view of the plastic/elastomeric gasket of FIG. 1, with a portion broken away;

#Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer to only the particular structure of the invention selected for illustration in the drawings, and are not intended to define or limit the scope of the invention.

#Referring initially to FIGS. 1, 1A, 2 and 3, the composite gasket 10 of the present invention comprises a first axially disposed portion 12 formed of an elastomeric material and a second axially disposed portion 14 adjacent the first axially disposed portion 12 formed of a generally non-flexible, non-elastomeric material plastic. As shown more particularly in FIGS. 1A and 2, the first axially disposed portion formed of elastomeric material has a leading edge 16 and a concave trailing edge or pocket 18. The first elastomeric portion also is provided with a sealing lip 20 extending radially inwardly. Typically, the elastomeric portion 16 is formed of a thermoplastic elastomeric resilient material, such as a natural rubber, synthetic rubber, including styrene-butadiene copolymer, neoprene, buty rubber, nitrile rubber, silicone rubber and the like, a blend of natural and synthetic rubbers, but preferably, a thermoplastic elastomer which will comply with specifications for elastomeric gaskets for joining plastic pipe, such as those, for example, provided by ASTM standard specifications, such as ASTM Specification F477-96a, published November 1996. A suitable thermoplastic elastomer is, for example, commercially available under the name "Santoprene" commercially available from Monsanto and "Thermolast K" compound TC 6 C AA commercially available from Gummiverk Kraiburg Elastik GmbH.

#The first axially disposed elastomeric portion 12 is joined to a second axially disposed portion 14. The second portion comprises multiple axially extending, laterally spaced ramp-like projections or ribs 24 separated by circumferential valleys 26. The non-elastomeric portion 14 comprising the ramp-like projections or ribs 24 is formed of substantially non-flexible or hard plastic for use in forming portion 14 and may include polyolefins, such as polyethylene or polypropylene, poly(vinylchloride), and the like materials which are usually synthetic, thermoplastic polymers and capable of being processed by extrusion, molding, etc., but which are not capable of rapidly returning to the original length after being significantly stretched, which can be adhered or preferably fused to the elastomeric portion 12 in a single molding step. Suitable plastic useful for the hard plastic portion and the elastomeric portion are disclosed in U.S. Pat. No. 4,693,483 to Valls and in U.S. Pat. No. 4,723,905 to Vassallo and Valls, the entire disclosures of which are hereby incorporated by reference.